Spike tires or chained tires for driving snow and ice covered roads have been used on vehicles. This, however, causes environmental problems such as dust pollution, and therefore studless tires have been developed. Studless tires have been improved in their materials and designs. For example, a rubber composition that contains a large amount of mineral oil and diene rubber having excellent low-temperature properties is used. However, if the amount of mineral oil is increased, the abrasion resistance usually deteriorates.
Meanwhile, along with the recent global warming, vehicles with studless tires are driven increasingly on paved roads. Therefore, improvement in total performance including dry performance and wet performance of studless tires is demanded. In particular, improvement in wet performance of tires is strongly demanded as it affects the safety of driving. On the other hand, further improvement in performance on snow and ice of tires is demanded, and thus the glass transition temperature of tread rubber compositions tends to be set low. In this case, it is difficult to simultaneously secure the wet performance. Thus, it is difficult for the conventional art to improve the performance on snow and ice, wet performance, and abrasion resistance in good balance.
Patent Documents 1 to 3 disclose rubber compositions including epoxidized polyisoprene, epoxidized natural rubber, or the like. However, the rubber compositions are not intended to improve the performance on snow and ice. Further, the rubber compositions are insufficient means for improving the performance on snow and ice, wet performance, and abrasion resistance in good balance.
Patent Document 1: JP 2006-188571 A
Patent Document 2: JP 2006-348222 A
Patent Document 3: JP 2008-303332 A